Slow expansion type profile control agent particle with triple cross-linked network structure and preparation method of slow expansion type profile control agent particle
By constructing a profile control agent particle with a triple network structure of chemical cross-linking-PVA crystallization region-hydrophobic association, the problem of expansion instability of pre-cross-linked particles in medium-high temperature and high-salt reservoir environments was solved, achieving controllable initial expansion, long expansion cycle and high-strength sealing effect, which is suitable for deep profile control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-07
AI Technical Summary
Existing pre-crosslinked particles expand too quickly in medium-high temperature and high-salt reservoir environments, resulting in high brittleness after expansion. It is difficult to coordinate the mechanical properties and expansion behavior, and the physical crosslinking network is prone to failure, leading to a sudden increase in injection pressure and a decrease in long-term sealing ability.
A triple cross-linking structure is adopted, consisting of a chemical cross-linking network, a highly ordered crystalline region of PVA, and a hydrophobic associative physical network. A dense hydrogen-bonded crystalline region is formed by drying at 120℃, which synergistically regulates the expansion behavior and mechanical properties, thereby constructing profile control agent particles with controllable initial expansion, long expansion cycle, and temperature and salt resistance.
It achieves low initial expansion rate and long expansion cycle in medium-high temperature and high salinity reservoirs, and possesses high strength and high toughness after expansion. It is suitable for deep profile control, avoids premature plugging in the near-wellbore zone, and significantly improves the long-term plugging effect.
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Abstract
Description
Technical Field
[0001] This invention relates to a slow-expanding profile control agent particle with a triple cross-linked network structure and its preparation method, belonging to the field of oilfield chemical technology, and is particularly suitable for profile control operations in medium- and high-temperature, high-salinity reservoirs. Background Technology
[0002] In oilfields in the later stages of water injection development, inter- and intra-layer heterogeneity intensifies, and dominant water drive channels develop, leading to premature water breakthrough and a continuous increase in water cut in high-permeability layers, while the utilization rate of medium- and low-permeability layers remains low, severely restricting overall oil recovery. Profile control and water shut-off technology, by selectively blocking high-permeability channels and regulating the injection profile, is an important means to improve water drive efficiency and increase oil recovery.
[0003] Currently, the commonly used profile control systems in oilfields mainly include underground gel-forming gels and pre-crosslinked expanded particles. Among them, pre-crosslinked particles, because they are synthesized and crosslinked on the surface, avoid the problems caused by environmental factors such as formation temperature, salinity, and pH that affect underground gel formation. They have good storage stability and adjustable particle size and have been widely used in the field. However, existing pre-crosslinked particles are mainly based on acrylamide homopolymers or copolymers, which have the following significant drawbacks: First, the expansion kinetics are difficult to control. Most particles rapidly absorb water and expand within hours of contact with water, easily forming a tight seal in the near-wellbore area, causing a sudden increase in injection pressure and restricting the migration to deep high-permeability channels. Second, it is difficult to optimize mechanical properties and expansion behavior in a coordinated manner. To improve strength, a high chemical crosslinking density is usually required, but this leads to increased material brittleness and insufficient elasticity, weakening its deformation sealing and fluid flow diversion capabilities in pore throats. Third, the physical crosslinking mechanism is singular and lacks stability. For example, relying solely on the hydrogen bond network of polyvinyl alcohol (PVA) can achieve a certain degree of slow expansion, but under high temperature (>80℃) or high mineralization conditions, the hydrogen bonds are easily affected by thermal disturbances or ion shielding effects and partially dissociate, resulting in a decrease in the slow expansion effect and a decline in long-term sealing ability.
[0004] In recent years, although some studies have attempted to improve performance by introducing inorganic fillers (such as calcium carbonate) or constructing dual-network structures (such as PVA / PAM), the fundamental contradiction between slow expansion, high strength, and high elasticity has not yet been resolved. In particular, there is a lack of a profile-adjusting particle system that can achieve controllable initial expansion, extended expansion period, and high strength and high toughness after expansion through multiple physical / chemical synergistic effects in medium-high temperature and high-salt reservoir environments.
[0005] Therefore, developing a slow-expanding profile control agent particle that simultaneously possesses a triple network structure of chemical crosslinking, hydrophobic association, and PVA crystallization region, with controllable expansion behavior, excellent mechanical properties, and good temperature and salt resistance, is of great significance for achieving deep profile control and improving the efficiency of oilfield development. Summary of the Invention
[0006] To address the shortcomings of existing technologies, especially the problems of excessively rapid initial expansion, high brittleness in the later stages of expansion, difficulty in synergistically controlling mechanical properties and slow expansion behavior of existing pre-crosslinked swellable particles, and the easy failure of physical crosslinking networks in medium-high temperature and high-salinity oil reservoir environments, this invention provides a slow-expanding profile control particle with a triple crosslinking network structure and its preparation method.
[0007] The slow-swelling profile control agent particles of this invention, with a triple cross-linked network structure, achieve synergistic regulation of slow swelling and mechanical properties through the combined effects of a chemical cross-linking network (covalent bonds), highly ordered PVA crystalline regions, and a hydrophobic associative physical network (constructed by the self-assembly of water-soluble hydrophobic monomers). The PVA crystalline regions are induced by a drying process at 80–120℃. Under 120℃ drying conditions, the PVA molecular chains exhibit a higher degree of ordered stacking, forming more dense and stable hydrogen-bonded crystalline regions. These regions serve as rigid physical cross-linking points, significantly promoting the inhibition of initial swelling and improving the long-term mechanical stability of the gel. Furthermore, this slow-swelling profile control agent has a low initial swelling ratio, a long swelling period, and exhibits both high strength and high toughness after swelling, along with good temperature and salt resistance, making it suitable for deep profile control needs in medium-high temperature and high-salinity oil reservoirs.
[0008] The present invention achieves the above objectives through the following technical solution: The first objective of this invention is to provide a slow-expanding profile control agent particle with a triple cross-linked network structure.
[0009] A slow-swelling profile control agent particle with a triple cross-linked network structure, wherein the slow-swelling profile control agent particle is prepared from the following raw materials in the following mass percentages: 15-25% water-soluble monomer, 0.5-1% functional monomer, 0.8-1.2% water-soluble hydrophobic monomer, 9-11% reinforcing agent, 0.10-0.20% cross-linking agent, 0.07-0.24% oxidation initiator, 0.03-0.12% reduction initiator, and the balance being deionized water.
[0010] According to the present invention, preferably, the water-soluble monomer is acrylamide.
[0011] According to the present invention, preferably, the functional monomer is sodium acrylate or sodium 2-acrylamido-2-methylpropanesulfonate.
[0012] According to the present invention, preferably, the water-soluble hydrophobic monomer is octylphenol polyoxyethylene ether acrylate.
[0013] According to the present invention, preferably, the reinforcing agent is polyvinyl alcohol 1788 or polyvinyl alcohol 1799.
[0014] According to the present invention, preferably, the crosslinking agent is N-hydroxymethylacrylamide or N,N'-methylenebisacrylamide.
[0015] According to the present invention, preferably, the oxidation initiator is ammonium persulfate or potassium persulfate.
[0016] According to the present invention, preferably, the reduction initiator is sodium bisulfite or sodium sulfite.
[0017] A second objective of this invention is to provide a method for preparing the above-mentioned slow-swelling profile control particles having a triple cross-linked network structure.
[0018] According to the present invention, the preparation method of the above-mentioned slow-swelling profile control agent particles having a triple cross-linked network structure includes the following steps: 1) Add the reinforcing agent to deionized water according to the ratio, heat and stir, and cool to room temperature to obtain the reinforcing agent solution; 2) According to the ratio, under stirring conditions, add water-soluble monomer, functional monomer, water-soluble hydrophobic monomer, crosslinking agent, oxidation initiator and reduction initiator to the reinforcing agent solution in sequence, mix evenly, and then carry out crosslinking reaction to obtain gel; 3) After the reaction is complete, the gel obtained from the reaction is granulated, dried and crushed to obtain slow-swelling profile control agent particles.
[0019] According to a preferred embodiment of the present invention, in step 1), the heating and stirring is performed by heating to 90-100°C and stirring for 1-4 hours.
[0020] According to a preferred embodiment of the present invention, in step 2), the crosslinking reaction temperature is 10-20°C, more preferably 15°C, and the reaction time is 4-6 hours, more preferably 5 hours.
[0021] According to a preferred embodiment of the present invention, in step 3), the drying temperature is 100-120°C; more preferably, the drying temperature is 120°C.
[0022] The slow-swelling profile control particles obtained by this invention possess three cross-linking mechanisms, thus exhibiting a triple cross-linking network structure: I. The covalent chemical cross-linking network formed by the cross-linking agent provides long-term structural stability; Second, the ordered crystalline regions formed by the reinforcing agent (polyvinyl alcohol) through high-temperature drying treatment serve as rigid physical cross-linking points, effectively inhibiting the rapid penetration of water molecules in the initial stage. Third, the hydrophobic association structure formed by water-soluble hydrophobic monomers can block the entry of water molecules in the dry state and in the early stage of water absorption, thereby effectively delaying the initial swelling rate of the particles.
[0023] The above-mentioned slow-expansion profile control agent particles with a triple cross-linked network structure are prepared by mixing the crushed particles with water on-site according to the preparation requirements of the on-site construction plan to obtain a slow-expansion profile control agent, which is suitable for profile control operations in medium-high temperature and high salinity reservoirs.
[0024] The technical features and effects of this invention are as follows: 1. The slow-expansion profile control agent of the present invention constructs a chemical cross-linking-PVA crystallization region-hydrophobic association triple network structure, which breaks through the performance bottleneck of traditional dual network systems (such as PVA / PAM) and achieves synergistic optimization of controllable initial expansion, extended expansion period and long-term mechanical stability.
[0025] 2. This invention introduces water-soluble hydrophobic monomers and PVA, and uses high-temperature drying for crystallization, which significantly reduces the initial swelling rate of the slow-swelling profile control agent. The initial swelling ratio is low and adjustable, and the swelling ratio can be controlled at 2 to 3 times in 24 hours, effectively avoiding premature plugging of the near-wellbore area. 3. The slow-expanding profile control agent of the present invention has a long expansion cycle. It can sustain stable expansion for up to 90 days under conditions of 85°C and 20,000 mg / L of mineralization. After expansion, it has both high strength and high toughness. The storage modulus of the expanded gel can reach more than 50 Pa after 90 days under conditions of 85°C and high mineralization. It has a stable structure and no obvious disintegration or dehydration. 4. The slow-expansion profile control agent system of the present invention does not contain inorganic fillers (such as calcium carbonate), has a uniform particle structure, and is suitable for deep sealing of low-permeability reservoirs and micro-fractures. 5. The slow-expansion profile control agent of the present invention adopts a low-temperature (10-20℃) oxidation-reduction initiation system, which has uniform polymerization, low energy consumption, and easy industrial scale-up.
[0026] 6. The slow-expansion profile control agent of the present invention has good temperature and salt resistance stability and is suitable for deep profile control needs in medium-high temperature and high salinity reservoirs. Detailed Implementation
[0027] Example 1 The preparation method of slow-swelling profile control agent particles with a triple cross-linked network structure includes the following steps: 1) Dissolve 22.5g of polyvinyl alcohol 1799 in 153.3g of deionized water, heat to 95℃ and stir for 2h, then cool to room temperature to obtain a 12.8% reinforcing agent solution; 2) Place the reinforcing agent solution in a reaction vessel and start stirring; then add 48g of acrylamide, 1.2g of sodium 2-acrylamido-2-methylpropanesulfonate, 1.83g of octylphenol polyoxyethylene ether acrylate (0.8wt%), 0.27g of N,N'-methylenebisacrylamide, 0.18g of ammonium persulfate, and 0.09g of sodium sulfite in sequence. After mixing evenly, react at 15℃ for 5h to obtain an elastic gel. Granulate the obtained gel, dry it at 120℃ to constant weight, and pulverize it to obtain slow-swelling profile control agent particles with a triple cross-linked network structure.
[0028] Example 2 The preparation method of slow-swelling profile control agent particles with a triple cross-linked network structure includes the following steps: 1) Dissolve 22.5g of polyvinyl alcohol 1799 in 153.3g of deionized water, heat to 95℃ and stir for 2h, then cool to room temperature to obtain a 12.8% reinforcing agent solution.
[0029] 2) Place the reinforcing agent solution in a reaction vessel and start stirring; then add 48g of acrylamide, 1.2g of sodium 2-acrylamido-2-methylpropanesulfonate, 2.75g of octylphenol polyoxyethylene ether (10) acrylate (1.2wt%), 0.27g of N,N'-methylenebisacrylamide, 0.18g of ammonium persulfate, and 0.09g of sodium sulfite in sequence. After mixing evenly, react at 15℃ for 5h to obtain an elastic gel. Granulate the obtained gel, dry it at 120℃ to constant weight, and pulverize it to obtain slow-swelling profile control particles with a triple cross-linked network structure.
[0030] Comparative Example 1 The preparation method is the same as that described in Example 1, except that: Without adding the water-soluble hydrophobic monomer octylphenol polyoxyethylene ether acrylate, the rest was carried out as in Example 1. The resulting gel was granulated, dried at 120°C to constant weight, and pulverized to obtain profile control agent particles.
[0031] Comparative Example 2 The preparation method is the same as that described in Example 2, except that: The obtained gel was granulated, dried at 60°C to constant weight, and pulverized to obtain profile control agent particles. Other procedures were carried out according to Example 1.
[0032] Experimental Example: Performance Testing 1. Test conditions Medium: Simulated formation water (mineralization 20,000 mg / L, containing Ca) 2+ / Mg 2+ 1500 mg / L) Temperature: 85℃ (representing a medium-high temperature oil reservoir) Testing period: 90 days 2. Testing Methods To verify the performance advantages of the slow-swelling profile control particles of the present invention, the particles obtained in Examples 1 and 2, and Comparative Examples 1 and 2, were evaluated under simulated reservoir conditions. The specific test methods are as follows: (1) Determination of expansion ratio Weigh 1.0 g (accurate to 0.01 g) of the dry granules from Examples 1, 2, 1, and 2, and Comparative Examples 1 and 2, and place them in 100 mL of simulated formation water (mineralization 20,000 mg / L, containing Ca). 2+ / Mg 2+(≈1500 mg / L), sealed and placed in an 85℃ constant temperature oven. Remove after 24 hours, 7 days, and 90 days, gently blot dry with filter paper, and weigh. The expansion ratio is calculated using the formula: Expansion ratio = Mass of expanded particles / Mass of dry particles (2) Determination of gel strength Take the profile control agent that has swollen for 90 days and test its gel strength at 85℃ according to the industry standard SYT 6296-2013 "Determination of the strength of gel for oil production by rheological parameters".
[0033] (3) Observation of appearance stability Visually record whether the gel particles disintegrate, pulverize, dehydrate and shrink, or adhere to the surface after 90 days.
[0034] The test results are shown in Table 1 below: Table 1 Performance data of slow-expanding granules at 85℃ and 20000 mg / L mineralization.
[0035] 3. Results Analysis The slow-swelling profile control particles prepared in Examples 1-2 exhibited excellent slow-swelling properties and long-term mechanical stability under simulated reservoir conditions (85℃, 20000 mg / L salinity). Comparison with Comparative Examples 1 and 2 fully verified the technical advantages of the triple cross-linked network structure of this invention; specifically as follows: (1) The initial expansion ratio is significantly reduced, effectively avoiding near-wellbore blockage. Comparative Example 1 (without hydrophobic monomer, dried at 120℃): The expansion ratio was as high as 4.8 after 24 hours, indicating that the PVA crystallization zone alone could not effectively inhibit the initial water molecule penetration. Example 1 (0.8% hydrophobic monomer, dried at 120°C): The expansion ratio decreased to 2.3 after 24 hours, indicating a low initial expansion ratio; The comparison reveals that the hydrophobic associative network formed by octylphenol polyoxyethylene ether acrylate introduced in this invention constitutes an effective "hydrophobic barrier" in the dry state and the initial water absorption stage. This is the key to achieving ultra-low initial expansion (the expansion ratio can be controlled within about 3 times in 24 hours), which can effectively prevent particles from blocking the near-wellbore area too early and ensure their migration to the deep high-permeability channels.
[0036] (2) The expansion process is continuous and stable, which meets the requirements of deep profile adjustment. The final expansion ratios of Examples 1 and 2 were 12.9 and 10.5, respectively, which were lower than the expansion ratio of 26.2 of Comparative Example 1. This indicates that the present invention achieves controllable expansion rather than unlimited swelling through the synergistic effect of the triple network, which is more conducive to forming a stable seal in the pore throat.
[0037] (3) The energy storage modulus decreases reasonably over time, but its long-term strength is still significantly better than that of the comparative example. Comparative Example 1 has a storage modulus of only 6 Pa after 90 days, and its structure has become severely loose. Comparative Example 2 has a storage modulus of 18 Pa at 90 days. Although it contains hydrophobic monomers, the PVA crystal region development is insufficient due to drying at 60℃, the density of physical crosslinking points is low, and the strength decays quickly. Example 1 achieved a storage modulus of 52 Pa at 90 days, which is 766.7% higher than that of Comparative Example 1, while maintaining a smooth appearance and good elasticity. Example 2 achieved a storage modulus of 63 Pa at 90 days, which is 250% higher than that of Comparative Example 2. It has a complete structure and strong resistance to disturbances.
[0038] (4) Significant impact of high-temperature drying process on material properties Comparative Example 2 (1.2% hydrophobic monomer, dried at 60°C) and Example 2 (1.2% hydrophobic monomer, dried at 120°C) have the same hydrophobic monomer content, but different drying temperatures. The 24-hour storage modulus (105 Pa) of Example 2 is much higher than that of Comparative Example 2 at 24 hours (48 Pa), and the 90-day storage modulus (63 Pa) is also significantly higher than that of Comparative Example 2 at 90 days (18 Pa).
[0039] Experimental results show that under drying conditions at 120℃, PVA molecular chains can undergo more complete ordered stacking, forming a denser and more stable hydrogen bond crystalline region. As a rigid physical crosslinking point, it works synergistically with the hydrophobic association network to significantly promote the overall strength and long-term stability of the material.
[0040] This invention successfully solves the technical problems of existing pre-crosslinked particles, such as rapid initial expansion, high brittleness in the later stage, and performance degradation under high temperature and high salt conditions, by constructing a chemical crosslinking-PVA crystallization region-hydrophobic association triple network structure and combining it with a 120℃ high-temperature drying process.
Claims
1. A slow-swelling profile control agent particle with a triple cross-linked network structure, wherein the slow-swelling profile control agent particle is prepared from the following raw materials in the following mass percentages: 15-25% water-soluble monomer, 0.5-1% functional monomer, 0.8-1.2% water-soluble hydrophobic monomer, 9-11% reinforcing agent, 0.10-0.20% cross-linking agent, 0.07-0.24% oxidation initiator, 0.03-0.12% reduction initiator, and the balance being deionized water.
2. The slow-expansion profile control granules according to claim 1, characterized in that, The water-soluble monomer is acrylamide.
3. The slow-expansion profile control granules according to claim 1, characterized in that, The functional monomer is sodium acrylate or sodium 2-acrylamido-2-methylpropanesulfonate.
4. The slow-expansion profile control granules according to claim 1, characterized in that, The water-soluble hydrophobic monomer is octylphenol polyoxyethylene ether acrylate.
5. The slow-expansion profile control granules according to claim 1, characterized in that, The reinforcing agent is polyvinyl alcohol 1788 or polyvinyl alcohol 1799.
6. The slow-expansion profile control granules according to claim 1, characterized in that, The crosslinking agent is N-hydroxymethylacrylamide or N,N'-methylenebisacrylamide.
7. The slow-expansion profile control granules according to claim 1, characterized in that, The oxidation initiator is ammonium persulfate or potassium persulfate, and the reduction initiator is sodium bisulfite or sodium sulfite.
8. A method for preparing slow-swelling profile control particles with a triple cross-linked network structure as described in any one of claims 1-7, comprising the following steps: 1) Add the reinforcing agent to deionized water according to the ratio, heat and stir, and cool to room temperature to obtain the reinforcing agent solution; 2) According to the ratio, under stirring conditions, add water-soluble monomer, functional monomer, water-soluble hydrophobic monomer, crosslinking agent, oxidation initiator and reduction initiator to the reinforcing agent solution in sequence, mix evenly, and then carry out crosslinking reaction to obtain gel; 3) After the reaction is complete, the gel obtained from the reaction is granulated, dried and crushed to obtain slow-swelling profile control agent particles.
9. The preparation method according to claim 8, characterized in that, In step 1), heating and stirring are performed at 90-100℃ for 1-4 hours. In step 2), the cross-linking reaction temperature is 10-20℃ and the reaction time is 4-6 hours. In step 3), the drying temperature is 100-120℃.
10. The application of the slow-expansion profile control agent particles with a triple cross-linked network structure as described in any one of claims 1-7, wherein the particles are mixed evenly with water on site according to the preparation requirements of the on-site construction plan to obtain the slow-expansion profile control agent, which is suitable for profile control operations in medium-high temperature and high salinity reservoirs.